美国债务超39万亿首破GDP：2026年，每位投资者都必须面对的“灰犀牛”

Key data: Total national debt ~$39 trillion · Debt-to-GDP ratio 100.2%, first time since WWII · FY2026 interest expense $1.039 trillion · Annual deficit ~$2 trillion · CBO projects debt to reach 175% of GDP by 2056 · Debt increasing by $5 to $8 billion daily

Section 1 — An Uncelebrated Historical Milestone

In March 2026, the United States crossed a threshold not seen in peacetime since the end of World War II. Government debt owed to external creditors — known as "debt held by the public," excluding obligations to internal government trust funds like Social Security — reached $31.27 trillion. Over the same period, nominal U.S. GDP over the past twelve months stood at $31.22 trillion. The debt-to-GDP ratio officially exceeded 100%.

Maya MacGuineas, President of the Committee for a Responsible Federal Budget, put it bluntly: "It has happened — U.S. national debt now exceeds the size of the entire U.S. economy and is roughly double the historical average."

According to U.S. Treasury data as of May 18, 2026, the total national debt stands precisely at $39,008,999,901,378.68. This figure increases by approximately $5 to $8 billion daily, with an average daily increase of about $7.5 billion over the past twelve months. The debt crossed $1 trillion in 1981, $10 trillion in 2008, and $20 trillion in 2017, nearly doubling in the last eight years.

Phillip Swagel, Director of the Congressional Budget Office, issued a stark warning in February 2026: "Our budget projections consistently indicate that the current fiscal trajectory is unsustainable." Under current law, federal debt will surpass the all-time high of 106% of GDP set at the end of WWII in 1946 before 2030. It is projected to reach 120% of GDP by 2036 and a staggering 175% by 2056. Unlike the post-WWII era, when robust growth and fiscal discipline gradually reduced the debt burden, there are no signs of a natural contraction in the current debt level.

Educational note: National debt is typically discussed in two ways. "Gross debt" covers all federal government obligations, including those to internal trust funds like Social Security. "Debt held by the public" refers to government debt owed to external creditors — investors, foreign governments, and financial institutions that buy Treasury securities. The latter is more economically significant as it represents actual external borrowing. Both metrics are currently at their highest peacetime levels in history.

Section 2 — Why the Debt Has Become So Intractable

The U.S. debt problem didn't erupt suddenly; it is the result of decades of cumulative structural choices — successive rounds of tax cuts without corresponding spending reductions, rising expenditures without matching revenue sources, compounded by the effects of interest on interest. Understanding this history helps explain why solving the problem is so difficult.

The structural gap between government spending and revenue. Since 1970, the U.S. federal government has run a budget surplus in only four years; it has been in deficit every other year. Whenever government spending exceeds tax revenue, the difference is covered by issuing debt. These bonds accumulate to form the debt, and the interest expense generated by the annual deficits further worsens the deficit. It is a compounding spiral.

Three major drivers of spending growth. The federal budget has three dominant and persistently growing expenditure centers. Social Security spending reached $953 billion in the first seven months of FY2026. Medicare spending over the same period was $588 billion. Net interest on public debt was $628 billion over these seven months, exceeding the combined spending on Medicare and Medicaid. These three categories are structural in nature, driven by demographic aging trends, healthcare costs, and debt accumulation, rather than annual political decisions. Cutting any one of them requires politically painful choices that successive administrations have long avoided.

The interest trap. This is the most worrying dynamic within the entire debt predicament. In 2015, the U.S. paid $223 billion in net interest on debt; in 2020, $345 billion; in 2024, $881 billion; in FY2026, it is projected to pay $1.039 trillion — nearly tripling in just six years. Interest payments have become the third-largest item in the federal budget, trailing only Social Security and Medicare, and surpassing defense spending. The CBO predicts that by 2028, interest spending will exceed Medicare spending, and by 2048, it will become the single largest line item in the federal budget — meaning the government will spend more on servicing its past debts than on all future investments combined.

The CBO projects that over the next 30 years, U.S. government interest payments alone will total nearly $100 trillion. To put this in perspective, this figure exceeds the combined spending of all major federal programs.

The One Big Beautiful Bill — the latest accelerant. The One Big Beautiful Bill (OBBB), signed into law in 2025, permanently extended the 2017 Trump-era tax cuts and added tax exemptions for tips and overtime pay. The CBO estimates the legislation will increase the fiscal deficit by $2.8 trillion over the next decade. If all temporary provisions were made permanent, the Committee for a Responsible Federal Budget estimates the cost could rise to $4 to $5 trillion. Projected cumulative deficits from 2026 to 2035 have now been revised up to $23.1 trillion, $1.4 trillion higher than the CBO's forecast from one year earlier.

The pandemic legacy. The two largest annual fiscal deficits in U.S. history occurred during the COVID-19 pandemic: $3.1 trillion in FY2020 and nearly $2.8 trillion in FY2021. These borrowings remain on the balance sheet and generate ongoing interest costs at interest rates far higher than the near-zero rates at which the debt was originally issued.

Educational note: A fiscal deficit is the annual difference between government spending and tax revenue. The national debt is the cumulative total of past deficits, plus all accrued interest. In simple terms: If you spend $5,000 more each month than you earn and use a credit card to cover the shortfall, your monthly deficit is $5,000. Your total debt is your credit card balance — each month's overspending added together, plus accumulating interest. The U.S. government's situation is exactly the same, just with many more zeros.

Section 3 — Can the U.S. Actually Go Bankrupt?

This is the question every retail investor eventually asks, and it deserves a careful and honest answer, not a simple yes or no.

The short answer is: The U.S. will not go bankrupt like a company or a household. The U.S. government issues its own currency — the U.S. dollar — and can, in theory, always create more dollars to pay its debts. Historically, no country that borrows in its own currency and controls its own central bank has ever been forced into involuntary default. The only time the U.S. defaulted was in 1979, and it was a brief default caused by a technical operational glitch.

But that doesn't mean there are no consequences. The ability to print money carries a different risk: inflation. If the U.S. government were to create large amounts of money to pay its debts, the purchasing power of every dollar in circulation would be eroded — essentially an implicit tax on everyone holding dollars and dollar-denominated assets. This is why the question "Can the U.S. go bankrupt?" is far less relevant than the question "What are the consequences of the current trajectory?"

The insight of Reinhart and Rogoff. Carmen Reinhart and Kenneth Rogoff, in their landmark study of over 800 years of financial crises, "This Time Is Different: Eight Centuries of Financial Folly," found that debt crises often do not arrive gradually and predictably but erupt suddenly from a collapse in confidence. A country that appears to be managing its debt comfortably can suddenly find that investors stop buying its bonds, or demand much higher yields, making normal debt repayment impossible. The shift from sustainable to unsustainable can happen in months, not years.

The Cato Institute's framework — gradual, then sudden. The Cato Institute uses Hemingway's famous analogy about how people go bankrupt to describe the U.S. fiscal trajectory: gradually, then suddenly. Rational market participants can clearly see the unsustainability of the U.S. fiscal path from a distance, yet they continue buying U.S. Treasury bonds — until one day they stop. This sudden moment cannot be predicted in advance, but the underlying conditions that precipitate it are steadily accumulating.

What a real fiscal crisis would look like. A U.S. fiscal crisis would not resemble a company filing for bankruptcy. It would more likely manifest as a sudden, sharp spike in long-term Treasury bond yields — investors demanding higher compensation to continue lending. This would simultaneously increase borrowing costs across the entire economy — mortgages, corporate bonds, consumer credit all rising. Banks, pension funds, and insurance companies holding large amounts of Treasury bonds would face significant losses, potentially threatening their own solvency. The U.S. House Budget Committee has explicitly stated that, given the dollar's status as the global reserve currency, such a crisis would "almost certainly produce irreversible international repercussions."

The dollar's reserve currency status is both a buffer and a risk. More than half of the world's foreign exchange reserves are held in U.S. dollars, creating a structural global demand for the dollar and dollar-denominated assets, including U.S. Treasuries. This reserve currency status is the core reason the U.S. can sustain large fiscal deficits at lower interest rates than any other country — an advantage economists call the "exorbitant privilege." But this status is not permanent; it relies on global confidence in the strength of the U.S. economy and the robustness of its institutions. If this confidence erodes — as the IMF has warned it is, evidenced by the disappearance of the "safety premium" on U.S. bonds — this buffer will narrow.

Educational note: A reserve currency is a currency widely held by central banks and international institutions as a store of value and a medium for global trade settlement. The U.S. dollar accounts for approximately 58% of global foreign exchange reserves. This means that even when neither party in a transaction is American, trade between other countries is often settled in dollars. This creates a persistent global demand for the dollar, supporting the U.S.'s ability to finance its borrowing at interest rates below normal market levels. 

Section 4 — What This Means for Investors

The U.S. debt problem is not a distant theoretical risk. It is already tangibly impacting financial markets and investor portfolios, and this influence is more likely to deepen than recede.

Direct link to rising yields. In just the second quarter of 2026, the U.S. Treasury needed to borrow $189 billion, $79 billion more than anticipated just a few months earlier. Actual borrowing in the first quarter of 2026 was $577 billion, and the third quarter is expected to require $671 billion. Such a massive and growing supply of Treasury bonds hitting the market can only attract enough buyers by offering higher yields. The 30-year Treasury yield has risen to 5.2%, the highest since 2007; the 10-year yield touched 4.687% on May 19th. These are not coincidences, but a direct reflection of supply-demand imbalance driven by government borrowing needs in the bond market.

Crowding out of private investment. When the government borrows heavily, it competes with businesses and households for available capital. As government borrowing expands, it raises borrowing costs for everyone — mortgage rates, corporate bond yields, auto loan rates, and credit card interest all increase. This suppresses private investment, slows economic growth, and constrains consumer spending. Funds that could have been directed towards roads, research, education, and defense instead flow to creditors in the form of debt service payments.

The self-reinforcing compounding dynamic. The most dangerous feature of the current trajectory is its self-reinforcing nature: larger debt leads to higher interest costs; higher interest costs lead to larger deficits; larger deficits require more borrowing; more borrowing pushes yields higher; higher yields increase the interest burden on new debt. This cycle can maintain surface-level stability for a considerable time — until a critical tipping point is reached.

Moody's downgrade and its signal. In May 2025, Moody's downgraded the U.S. sovereign credit rating from Aaa to Aa1, becoming the last of the three major rating agencies to do so. S&P downgraded in 2011, and Fitch in 2023. The three agencies, acting over a span of 14 years, have conveyed the same message: the current fiscal trajectory is inconsistent with a top-tier credit rating, and the gap between government commitments and revenue is structural, not cyclical.

Social Security solvency — the 2032 deadline. The CBO projects that the Social Security Old-Age and Survivors Insurance (OASI) trust fund will be exhausted by 2032, one year earlier than previously forecast. If Congress does not act by then, according to the latest calculations from the Committee for a Responsible Federal Budget based on CBO projections, benefits for all recipients would be automatically cut by approximately 28%. And current spending on Social Security has already reached $953 billion in the first seven months of FY2026 alone. Any legislative fix would involve politically painful choices that have been repeatedly postponed for decades.

Section 5 — If U.S. Debt Is Set to Explode, Why Isn't Anyone 'Defusing the Bomb'? 

Solving the U.S. debt problem is arithmetically simple but politically near-impossible. The mathematical solution is some combination of raising revenue and cutting spending. The political challenge is that either approach requires elected officials to ask voters to accept higher taxes or lower benefits — neither of which wins elections.

The revenue-side dilemma. Federal tax revenue has persistently fallen short of spending levels. Closing the deficit gap through tax increases would require raising income tax rates, broadening the tax base, or creating new revenue sources. The One Big Beautiful Bill heads in the exact opposite direction, cutting taxes and expanding exemptions.

The spending-side dilemma. Meaningful deficit reduction must eventually address the three major spending categories: Social Security, Medicare, and debt interest. Interest payments cannot be directly cut; they are a legal obligation on existing debt. Cutting Social Security and Medicare is politically toxic, directly affecting the largest and most politically active demographic in the country — retirees and those nearing retirement age.

The growth thesis. Some economists argue that robust economic growth is the most realistic path to reducing the debt-to-GDP ratio without explicit fiscal consolidation. If the economy grows faster than debt consistently, the ratio will eventually stabilize. This is effectively what happened in the decades following WWII. Counterarguments note that the current debt trajectory is too steep, interest costs are growing too fast, and growth alone is insufficient to solve the problem.

The consensus of fiscal watchdogs. The Committee for a Responsible Federal Budget estimates that stabilizing the debt would require roughly $10 trillion in deficit reduction. There is currently no prospect of bipartisan cooperation even approaching this scale. CBO Director Swagel's summary judgment — "the fiscal trajectory is unsustainable" — represents the consensus of nearly every nonpartisan fiscal institution in the country.

Educational note: The "debt-to-GDP ratio" is the standard metric economists use to assess a country's debt burden. It compares the total debt to the size of the economy, because sustainability depends on the economy's ability to service the debt, not just the absolute number. The U.S. debt-to-GDP ratio exceeding 100% means the debt is now larger than the entire annual output of the economy — a level previously seen only during World War II.

Section 6 — Impact on Different Types of Investors

**Equity Investors:** The debt crisis fosters a long-term interest rate environment significantly higher than the near-zero era of 2009-2022. This structurally pressures high-valuation growth stocks that rely on low discount rates. Benefiting sectors include financials — wider spreads boost interest income for banks and insurers — and companies with robust current earnings and low debt levels.

**Bond Investors:** The U.S. debt trajectory is a medium-term headwind for long-term Treasuries. Increased bond supply means price pressure and yields trending higher over time. For income-seeking investors, the current yield environment is the most attractive in nearly fifteen years — but the risk is that yields could continue to rise. Investment-grade corporate bonds and intermediate-term Treasuries currently offer a better risk-reward balance than long-term Treasuries in this environment.

**Gold and Real Asset Investors:** Historically, persistent fiscal deficits and currency debasement fears have been key drivers of gold demand. The significant appreciation of gold over the past two years partially reflects the market's assessment of the U.S. fiscal trajectory. Real assets — physical real estate, commodities, Treasury Inflation-Protected Securities (TIPS) — have historically provided some hedge against the erosion of purchasing power caused by fiscal excess.

**Singapore and Asian Investors:** The U.S. debt crisis affects Asia through multiple channels. Rising U.S. yields attract capital outflows from emerging markets, pressuring Asian currencies and stock markets. If a loss of confidence in U.S. fiscal management leads to a weaker dollar, the purchasing power of dollar-denominated assets held by Asian investors would be impaired. Singapore, as an international financial hub, is particularly sensitive to any global capital market turmoil triggered by U.S. fiscal stress.

**All Investors:** The most important practical implication of the current debt situation is that the era of ultra-low interest rates that prevailed from 2009 to 2022 will not return. The structural forces maintaining a high-interest-rate environment — the need for massive Treasury issuance to cover persistent deficits — are not temporary. Investment portfolio strategies built on the assumption of permanently cheap financing need to be re-evaluated and adjusted. 

Section 7 — An Honest Assessment: Crisis, Slow Burn, or Controllable Decline

Three broad scenarios exist for the evolution of the U.S. debt situation over the next decade.

**Scenario One: Gradual Stabilization.** Congress ultimately enacts substantive fiscal reform — a combination of revenue increases and spending controls — that stabilizes the debt-to-GDP ratio. This has precedent in other countries: the UK and Canada both undertook painful but successful fiscal consolidations in the 1990s. In this scenario, long-term yields eventually stabilize or even decline, allowing financial markets to adjust without a crisis.

**Scenario Two: Slow Burn.** Debt continues to grow, interest rates remain high, and potential economic growth is persistently pressured by government borrowing crowding out private investment. Inflation hovers above the Fed's target. Improvements in living standards slow. The U.S. retains its reserve currency status, but its premium narrows. Most fiscal economists view